The present invention relates to the packaging of integrated circuits (ICs) and more particularly to a heat spreader for a semiconductor package and a method of forming a semiconductor package with such a heat spreader.
Heat is generated by an IC die during operation. If inadequately removed, the heat generated by the die may cause the device to fail. As such, heat spreaders are often incorporated into semiconductor packages to improve the thermal performance of the package. For optimal thermal conduction, a heat spreader should ideally be attached to an IC die to provide a direct path for the heat from the die. Consequently, a number of semiconductor packages with heat spreaders attached to IC die surfaces have been proposed. A typical example of one such semiconductor package is described below with reference to FIG. 1.
FIG. 1 shows a conventional semiconductor package 10 having a stacked-on heat spreader 12. The semiconductor package 10 includes an IC die 14 having a bottom surface 16 attached to a substrate 18 with an adhesive material 20. The IC die 14 is electrically connected to the substrate 18 with a plurality of wires 22. The heat spreader 12 is attached to a top surface 24 of the IC die 14 with a thermal adhesive 26. A portion of the heat spreader 12, the IC die 14, a portion of the substrate 18 and the wires 22 are covered by a mold compound 28. To prevent bleeding or flashing of the mold compound 28 during mold transfer, which renders the heat spreader 12 ineffective, a significant clamping force (represented by bold arrows in FIG. 1) is exerted by a mold chase 30 on the heat spreader 12 during a molding operation. Because the heat spreader 12 is attached to the IC die 14, the clamping force exerted by the mold chase 30 on the heat spreader 12 is transmitted to the IC die 14. Consequently, the top surface 24 of the IC die 14 experiences significant compressive stress during the molding operation, which can cause the IC die 14 to crack. Thus, there is a need for a way to reliably manufacture semiconductor packages with heat spreaders attached to IC die surfaces.